Constitutive recycling of the store-operated Ca2+ channel Orai1 and its internalization during meiosis

T he egg's competency to activate at fertilization and transition to embryogenesis is dependent on its ability to generate a fertilization-specific Ca2+ transient To endow the egg with this capacity, Ca2+ signals remodel during oocyte maturation, including inactivation of the primary Ca2+ influx pathway store operated Ca2+ entry (SOCE) SOCE inactivation is coupled to internalization of the SOCE channel, rail In this study, we show that Orai1 internalizes during meiosis through a caveolin (Cav) and dynamin-dependent endocytic pathway Cav binds to Orai1, and we map a Cav consensus binding site in the rail N terminus, which is required for rail internalization Furthermore, at rest, Orai1 actively recycles between an endosomal compartment and the cell membrane through a Rho dependent endocytic pathway A significant percentage of total Orai1 is intracellular at steady state Store depletion completely shifts endosomal Orai1 to the cell membrane These results define vesicular trafficking mechanisms in the oocyte that control Orai1 subcellular localization at steady state, during meiosis, and after store depletion